The present invention generally relates to wood processing equipment and, more particularly, to an apparatus for transferring and singly loading elongated lumber pieces from a side-by-side relationship on a first conveyor to a second conveyor.
In typical sawmills, wherein raw wood is sawn mechanically into lumber pieces (i.e., planks, boards, etc.), much effort is spent in maximizing the productivity and output. Consequently, sawmills are increasingly automated in order to accelerate the speed of execution of the various tasks in the manufacturing of lumber pieces.
In one such task, lumber pieces which are disposed in side-by-side abutting relationship on a conveyor are singly spaced by being transferred to another conveyor. The spacing of the lumber pieces may, for instance, facilitate the individual sorting of the lumber pieces according to their quality.
U.S. Pat. Nos. 4,945,976, issued to Ritola on Aug. 7, 1990; U.S. Pat. No. 5,287,954, issued on Feb. 22, 1994 to Draghetti; U.S. Pat. No. 5,419,425, issued to Goater on May 30, 1995; U.S. Pat. No. 5,662,203, issued to St-Pierre et al. on Sep. 2, 1997; and U.S. Pat. No. 5,518,106, issued on May 21, 1996 to Allard, each disclose various apparatuses for transferring lumber pieces from a first conveyor to a second conveyor, thereby controlling the spacing therebetween. One of the goals of the apparatuses is to increase the speed and the reliability of the lumber piece transfer. However, as raw lumber is often bowed or twisted, and the corner edges are often bad due to wane, the reliability of the transfer decreases considerably as we attempt to increase the transfer speed. Most of these patents describe mechanisms which toss out pieces forward, with the result that the position and alignment of the lumber pieces on the outfeed conveyor is hard to control precisely, especially if the piece is warped, or slippery from being wet or iced.
A further patent, namely U.S. Pat. No. 5,813,512, issued on Sep. 29, 1998 to Andersson et al., also discloses an apparatus for spacing lumber pieces, but perhaps at a faster rate than the previously disclosed patents. This is achieved by a rotating wheel having a plurality of camming surfaces disposed at the junction of a pair of conveyors. A belt, extended between an idler pulley and a driver pulley, is generally positioned over the rotating wheel. A stop is located upstream of the rotating wheel so as to hold pieces of lumber fed by a first conveyor in a side-by-side relationship. Each of the camming surfaces of the rotating wheel is sized so as to lift a lumber piece above the stop and to pinch it against the belt. As the belt is resilient, the piece of lumber is held between the camming surface and the belt until the piece of lumber reaches the downstream second conveyor. It is pointed out that the rotating wheel and the belt, via the driver wheel, are both driven synchronously by a same motor, so as to have a same tangential speed at their periphery. Advantageously, lumber pieces travelling from a conveyor to another are held on both their bottom and top surfaces.
In order to maximize the rate in transferring and spacing of lumber pieces from a conveyor to another, a few design considerations are required. For one, the lumber piece has to be held securely, in at least two points on the lumber piece, at all times during the transfer. Another consideration is that the stop at the end of the infeed conveyor is sufficiently high to ensure an effective abutment of all the lumber pieces. However, the stop becomes an obstacle which the lumber pieces must surmount, thereby slowing the transfer process down. Furthermore, the lumber pieces ejected from the transfer apparatuses must stay perpendicular to the outfeed conveyor, whereby the operating speed of the transfer apparatuses is often slowed down when the lumber pieces being transferred are wet or iced to ensure this perpendicular positioning.
It is a feature of the present invention to provide an apparatus for transferring and singly loading elongated members from a first conveyor to a second conveyor which substantially overcomes the above-mentioned disadvantages.
According to the above feature of the present invention, and from a broad aspect thereof, the present invention provides an apparatus for singly loading perpendicularly conveyed elongated members from a first conveyor to a desired disposition on a second conveyor. The apparatus is positioned downstream of the first conveyor and upstream of the second conveyor. The apparatus comprises plural stopper arms each analogously displaceable between an abutting position, wherein the stopper arms hold elongated members from moving forward on the first conveyor, and a bypassing position, wherein the stopper arms are disposed below the first conveyor for allowing the elongated members to move forward as displaced by the first conveyor. Plural analogously moving lower loaders wheel each have a generally circular body with a gripping surface on an outer periphery thereof. The gripping surface is adapted for abutting an elongated member. Plural analogously moving upper loader wheels are generally positioned above the lower loader wheels and have a resilient peripheral portion. Plural stabilizer wheels are idle and adapted for lying on a top surface of an elongated members at least when the elongated member is abutted against the stopper arms. The apparatus is synchronized such that the elongated member is lifted by the gripping surfaces of the lower loader wheels when the stopper arms are moved to the bypassing position, whereby the elongated member is engaged between the gripping surfaces of the lower loader wheels and the stabilizer wheels or the resilient portions of the upper loader wheels while being transferred from the first conveyor to the second conveyor.